Automatic pilot system



Nov. 16, 1965 R. B. WALLACE 3,217,683

AUTOMATIC PILOT SYSTEM Filed March 16, 1964 INVENTOR.

RICHARD B. WA LLACE United States The present invention relates to improvements in an automatic pilot system for a boat, and more particularly, to means for sensitizing the control so as to enable the automatic pilot to maintain a required course or heading with greater accuracy.

The present invention constitutes an improvement in the system disclosed in \Vallace et a1. application Serial No. 211,617, filed July 23, 1962, now Patent No. 3,148,- 654, Sept. 15, 1964.

It is an object of the present invention to provide a support which is angularly adjustable about a vertical axis, a compass, pivot means mounting said compass on said support, and a sensitizing magnet movable with said support and having its magnetic field aligned with the earths magnetic field when said support is properly oriented with the earths magnetic field.

It is a further object of the present invention to provide structure as described in the preceding paragraphs in which the compass constitutes a valve member and in which the support relative to which the compass rotates is provided with valve port means.

In general, it is an object of the persent invention to provide a first member, a second member movable in either direction relative to said first member from an intermediate null position by an amount related directly to changes in the value of a parmeter from a predetermined value thereof, and sensitizing means operably associated with said second member responsive to movement of said second member and effective to produce a predetermined additional increment of motion of one of said members in the same relative direction.

It is a further object of the present invention to pro vide structure as defined in the preceding paragraph in which the sensitizing means is effective to provide for return of said members to null position when the value of said parameter returns to its said predetermined value.

It is a further object of the present invention to provide structure as described in the preceding paragraphs in association with steering mechanism for a boat, and more particularly, with fluid and preferably a vacuum motor for effecting movement of the boat rudder to correct the course heading.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing, illustrating a preferred embodiment of the invention, wherein:

FIGURE 1 is a .plan view of the control elements of the automatic pilot system.

FIGURE 2 is a fragmentary vertical section through a portion of the control system.

FIGURE 3 is a fragmentary enlarged view showing the relationship between the compass magnet and the sensitizing magnet.

Described in general terms, the present invention relates to an automatic pilot for a boat. As disclosed in the prior copending Wallace et a1. application identified above, the

atent 3,217,683 Patented Nov. 16, 1965 rudder of the boat has connected thereto a fluid motor, specifically, a vacuum motor effective to shift the rudder in either direction to bring the boat back to a required heading. The fluid motor is under the control of valve means associated with the compass.

Referring now specifically to FIGURES 1 and 2, the direction sensitive control means for the fluid motor comprises a support plate 10 received in a housing 12 having a cover 14. Extending through the plate 10 is a generally cylindrical annular barrel 16 which is provided with fluid passages in connection with external conduits 18 and 20. Rotatable within the barrel 16 is a spool 22 having valve ports 24 and 26 in its upper surface. These ports connect by suitable passages provided in the spool 22 and barrel 16 with the passages 18 and 20. Alternatively, of course, one port and passage may be omitted, and control exerted by a variable pressure or vacuum acting against a spring 01' the like.

As best seen in FIGURE 2, a compass card 28 is provided having an arcuate recessed edge portion 30 related to the valve ports 24 and 26, or one of them if both are not used, so as to provide equal or controlled partial closure thereof when the compass card is in an intermediate position with respect thereto. The card 28 carries a compass magnet or needle 31.

In practice, the passages 18 and 20 which communicate respectively with the ports 24 and 26, may be atmospheric bleed passages connecting to expansible vacuum chambers of the fluid motor. As relative angular movement about a central vertical axis takes place between the compass card 28 and the ports 24 and 26, these vacuum chambers are exposed unequally to atmospheric bleed so that one is effective to overcome the other and to thereby efi ect adjustment of the rudder. Where a single port is used, variable vacuum is applied to an expansible chamber which includes resilient biasing means.

The compass card 28 is reciprocated vertically b-y vertical movement of a support pin 32 the upper end of which is pointed to provide a needle bearing received in a bearing cup 34 on the compass card. Conveniently, vertical movement of the pin 32 is accom plished by a lever 36 pivoted at 38 and having a cam follower 4d engaging an oscillatable or rotatable cam 42. It will be appreciated that when the pin 32 is raised so that the compass 28 is spaced upwardly above the top surface of the spool 22, the compass is free for angular movement about the axis of the pin 32 in order to align itself with the earths magnetic field. Upon downward movement of the pin 32 the compass card engages the upper surface of the spool 22 and cooperates with the ports 24 and 26 to control the steering motor connected to the rudder.

In order to control the heading of the boat, the outline of which is suggested in dot-and-dash lines at 44 in FIG- URE 1, the spool 22 is provided with a gear 46 in mesh with a gear 48 keyed or otherwise secured to a shaft 50 in an opening 52 in the cover 14. Fixed to the upper end of the shaft 50 is an adjusting knob 54.

In order to understand the operation of the sensitizing means, reference is now made to FIGURE 3 wherein a portion of the compass card 28 is shown in association with the adjacent upwardly exposed top surface of the spool 22. The compass card 28 includes a compass magnet 31 having north and south poles as indicated. Carried by the upper surface of the spool 22 adjacent the edge thereof is a sensitizing magnet 66 having north and south poles as indicated. It is to be noted that the sensitizing magnet 66, while in line with magnet 31, has its poles reversed relative thereto.

It will of course be apparent that when the spool 22 is angularly adjusted to select the course, its valve ports 24 and 26 and its sensitizing magnet 66 are moved angularly with respect to the boat to a position in accordance with the selected heading. It will also be apparent of course that at this time, and in fact at all times, the compass card 28 remains substantially in a selected position in which the poles of the compass magnet are in alignment with the earths magnetic field.

Assuming that a course has been selected by setting the spool 22 and magnet 66 as desired, and that the boat 44 has been brought onto the required course, the conditions illustrated in FIGURE 3 will then prevail. The sensitizing magnet 66 is then in alignment with the earths magnetic field. The compass magnet 31 is in a magnetic north-south position in alignment with the earths magnetic field, and the shoulders at the ends of the arcuately reduced edge portion 30 of the compass card will be symmetrically spaced with respect to the adjacent valve ports 24 and 26. Accordingly, the pressures or vacuum in the expansible chambers communicating with the conduits 18 and are equal and the rudder is stationary in whatever position it has attained. If now, for some reason, the boat is caused to change its heading the spool 22 including the valve ports 24 and 26 and the sensitizing magnet 66 moves right or left from the position shown in FIGURE 3. The effect of this is to provide for unequal openings in the ports 24 and 26 and also to provide for lateral displacement of the sensitizing magnet 66 relative to the compass magnet 31. It has been found that a predetermined small displacement of the sensitizing magnet in one direction from north-south direction produces a predetermined displacement of the compass magnet in the opposite direction, thus increasing the displacement between the ported top surface of the spool 22 and the valving portions of the compass card 28.

The explanation of the operation of the sensitizing magnet in amplifying the signal produced by a departure from the selected heading of the boat apparently involves a localized distortion of the earths magnetic field which is effective to produce a corresponding displacement of the compass magnet. When the sensitizing magnet 66 is in the position illustrated in FIGURE 3, in alignment with the earths magnetic field and with its south pole at the north end of the magnet, the effect of this magnet on the earths magnetic field in its immediate vicinity is to somewhat diminish the strength of the earths magnetic field without however, producing any change in the direction of the lines of force of the earths magnetic field. However, when the sensitizing magnet is shifted by a change in heading of the boat to a position in which its longitudinal axis and hence its external field extends at .an angle to the earths magnetic field, the effect is to produce a localized resultant field which is displaced from a magnetic north-south direction by an amount depending in part on the strength of the sensitizing magnet and the direction at which its north-south axis extends with respect to the direction of magnetic north. The effect of this localized distortion of the earths magnetic field, or in other words, the creation of a resultant magnetic field disposed at an angle to the magnetic north-south direction, is to cause the compass needle or magnet to align itself with the resultant field. The effect on the compass magnet is of course variable in accordance with the distance from the compass needle at which the sensitizing magnet is placed. It is thus possible to control the sensitivity of the automatic pilot by controlling the distance between the sensitizing magnet and the magnet or needle of the compass card.

While the construction described in the foregoing represents perhaps the simplest way to obtain the desired result, it will be apparent that modifications of the physical arrangement of the magnetic means may be provided. Thus for example, instead of employing a single sensitizing magnet which occupies a position directly in northsouth alignment with the pivot of the compass needle, a pair of similar magnets may be positioned equally spaced at opposite sides of the north-south line passing through the pivot axis of the compass needle. These two magnets have a resultant field of their own which combines with the earths magnetic field to produce a resultant field which is angularly displaced from magnetic north-south when the boat departs from its pre-selected heading.

Similar results may be obtained by providing a single elongated magnet having its north-south poles in substantially the same horizontal plane as the compass card but at opposite sides thereof, these poles being in alignment with the magnetic north-south direction when the boat is on a proper heading.

Since the corrective action of the rudder is variably controlled by the relative displacement between valve ports 24 and 26 and the valving portions of the compass card, this means that a greater corrective action of the rudder takes place as a result of displacement of the compass card itself by the sensitizing magnet.

It has been found by extensive tests that as the boat resumes its selected course so that the sensitizing magnet approaches the center position directly south of the compass magnet pivot pin 34, the compass magnet 31 similarly approaches its correct nortl1-south position or the position in which its north-south poles are in alignment with the earths magnetic field.

Dependent upon variations in strength of the sensitizing magnet and its location relative to the path of movement of the adjacent pole of the compass magnet, the amount of displacement of the compass card due to the action of the sensitizing magnet can be selectively controlled.

The results of actual tests employing the equipment described in the foregoing is given below in tabular form. The first column headed, Rose Reading, gives the angular displacement of the sensitizing magnet, which in this instance resulted from moving the support or compass rose counterclockwise.

The second column entitled, Compass Reading, represents actual rcading of the compass with reference to graduations provided on the adjustable support or rose, resulting from displacement of the compass needle in a direction opposite to displacement of the compass rose.

The third column entitled, Additional Displacement From Magnetic North, represents the amount by which the resultant magnetic field at the location of the compass needle differs from magnetic north, and therefore represents additional displacement of the compass card relative to the support or rose.

Additional dis- Rose reading, Compass readplacement from degrees ing, degrees magnetic north,

degrees 1% 2% 1 2 3 1 4 6% 2% 6 1O 4 8 13 5 10 17 7 2O 30 10 30 42 12 4O 52 12 The results of this tabulation were checked by moving the compass card reversely to the indicated positions and the compass readings were duplicated exactly, a compass reading of zero being obtained when the setting of the compass rose to zero was restored.

A second test was run in which the sensitizing magnet was positioned somewhat closer to the compass magnet and these results are set forth in the table below:

Additional dis- Rose reading, Compass readplacement from degrees ing, degrees magnetic north,

degrees Again, in moving the rose back to the zero position in the same steps it was found that the compass readings duplicated exactly and that the compass reading of zero degrees was obtained when the compass rose was returned to its zero position.

It is important to note that as the boat heading is changed as a result of the controlled operation of the rudder, the displacement of the compass card by the sensitizing magnet diminishes as the boat resumes the correct course and there is no tendency for the sensitizing magnet to produce an over-correction or displace-ment of the compass card in the opposite direction. In .fact, as the boat approaches its pre-selected heading, the rudder moves towards the position required to maintain the selected heading and arrives substantially at the required position when the boat has assumed its proper heading. This of course prevents over-correcting or hunting with the resultant movement of the ship on a zigzag course.

It is to be noted that when movement of the rudder to required position is referred to, this does not necessarily mean that the rudder is amidship. The present automatic pilot system is effective to maintain the rudder in whatever position is necessary to keep the boat on its required course. Thus for example, with a cross Wind, it may in some cases be necessary to maintain substantial right or left rudder to maintain the boat steadily on a pre-selccted course.

It will of course be apparent that the sensitizing magnet 66 must be separated from the compass magnet 31 by a distance sufiicient to prevent the mutual repulsion between the like poles from exerting forces on the Compass magnet which would be eflective to prevent it returning to true magnetic north-south direction when the boat returns exactly to its selected magnetic heading.

The drawing and the foregoing specification constitute a description of the improved automatic pilot system in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

1. An automatic pilot system for a boat having a rudder and a pneumatic motor connected to said rudder, a

support adjustable about a vertical axis relative to said boat to determine a selected boat heading, an air passage connected to said motor having a control port on said support adjustable therewith about said vertical axis, a compass including a compass magnet mounted for swing ing movement about said vertical axis to maintain align ment with the horizontal component of the ambient mag netic field, said compass having valving means movable therewith in a horizontal plane in operative relation to said control port, a sensitizing magnet fixed to said support in such proximity to said compass magnet as to provide with the earths magnetic field a resultant field surrounding said compass magnet which difiers in direction from the earths magnetic field when the boat is on a heading different from the selected heading effective to displace the compass and its valving means in a direction opposite to movement of said support and the control port thereon to provide an amplified corrective operation of said motor.

2. A system as defined in claim 1 in which said sensitizing magnet is horizontal and is substantially displaced horizontally from said compass magnet and is positioned in horizontal alignment with said compass magnet when the boat is on its selected heading, the northern end of said sensitizing magnet being its south magnetic pole.

3. An automatic pilot system for a boat having a rudder and a pneumatic motor connected to said rudder, a support adjustable about a vertical axis relative to said boat to determine a selected boat heading, an air passage connected to said motor having a control port on said support adjustable therewith about said vertical axis, a compass comprising a generally circular card overlying said support and a compass magnet fixed to said card, pivot means mounting said card for angular movement about said vertical axis to maintain alignment with the horizontal component of the ambient magnetic field, a peripheral portion of said card being formed to constitute a valve cooperable with said port, said support extending laterally beyond said card, a sensitizing magnet carried by a portion of said support located laterally be yond the edge of said card in such proximity to said compass magnet as to provide with the earths magnetic field a resultant field surrounding said compass magnet, said sensitizing magnet having its north-south axis horizontal and in alignment with the north-south axis of said com pass magnet when the boat is on its selected heading, the northern end of said sensitizing magnet being its south magnetic pole.

References Cited by the Examiner UNITED STATES PATENTS 2,311,952 2/1943 Martin 33-222.5 3,148,654 9/1964 Wallace et a1. 114-144 MILTON BUCHLER, Primary Examiner.

ANDREW H. FARRELL, Examiner. 

1. AN AUTOMATIC PILOT SYSTEM FOR A BOAT HAVING A RUDDER AND A PNEUMATIC MOTOR CONNECTED TO SAID RUDDER, A SUPPORT ADJUSTABLE ABOUT A VERTICAL AXIS RELATIVE TO SAID BOAT TO DETERMINE A SELECTED BOAT HEADING, AN AIR PASSAGE CONNECTED TO SAID MOTOR HAVING A CONTROL PORT ON SAID SUPPORT ADJUSTABLE THEREWITH ABOUT SAID VERTICAL AXIS, A COMPASS INCLUDING A COMPASS MAGNET MOUNTED FOR SWING ING MOVEMENT ABOUT SAID VERTICAL AXIS TO MAINTAIN ALIGN MENT WITH THE HORIZONTAL COMPONENT OF THE AMBIENT MAGNETIC FIELD, SAID COMPASS HAVING VALVING MEANS MOVABLE THEREWITH IN A HORIZONTAL PLANE IN OPERATIVE RELATION TO SAID CONTROL PORT, A SENSITIZING MAGNET FIXED TO SAID SUPPORT IN SUCH PROXIMITY TO SAID COMPASS MAGNET AS TO PROVIDE WITH THE EARTH''S MAGNETIC FIELD A RESULTANT FIELD SURROUNDING SAID COMPASS MAGNET WHICH DIFFERS IN DIRECTION FROM THE EARTH''S MAGNETIC FIELD WHEN THE BOAT IS ON A HEADING DIFFERENT FROM THE SELECTED HEADING EFFECTIVE TO DISPLACE THE COMPASS AND ITS VALVING MEANS IN A DIRECTION OPPOSITE TO MOVEMENT OF SAID SUPPORT AND THE CONTROL PORT THEREON TO PROVIDE AN AMPLIFIED CORRECTIVE OPERATION OF SAID MOTOR. 